Desulfurization and conversion of black oils to maximize gasoline production



United States Patent O DESULFURIZATION AND CONVERSION OF BLACK OILS TOMAXIMIZE GASOLINE PRODUCTION Laurence R. Steenberg, Chicago, Ill.,assignor to Universal Oil Products, Company, Des Plaines, Ill., acorporation of Delaware Filed Sept. 26, 1967, Ser. No. 670,546 Int. Cl.Cg 7/00, 37/00 U.S. Cl. 208-93 6 Claims ABSTRACT OF THE DISCLOSUREAPPLICABILITY OF INVENTION The invention described herein is adaptableto a process for the conversion of petroleum crude oil, and heavierfractions derived therefrom, into lower boiling hydrocarbon products.More specifically, the present invention is directed toward a processfor converting atmospheric tower bottoms products, lvacuum tower bottomsproducts (Vacuum residuum), crude oil residuum, topped crude oils, crudeoils extracted from tar sands, etc., all of which are commonly referredto as black oils. In particular, the process herein defined alfords themaximum production of gasoline boiling range hydrocarbons from suchmaterial.

Petroleum crude oils, particularly the heavy oils extracted from tarsands, topped or reduced crudes, and vacuum residuum, etc. contain highmolecular weight sulfurous compounds in exceedingly large quantities. Inaddition, such crude, or black oils contain excessive quantities ofnitrogenous compounds, high molecular weight organo-metallic complexescomprising principally nickel and vanadium, and asphaltic material. Thehigh molecular weight asphaltic material is generally found to becomplexed with sulfur and, to a certain extent, with the organometalliccontaminants. Currently, an abundant supply of such hydrocarbonaceousmaterial exists, most of which has a gravity less than 25.0 API, and asignificant quantity of which has a gravity less than 10.0 API. Thismaterial is generally further characterized by a boiling rangeindicating that 10% by volume, and very often more, boils above atemperature of about 1050 F. The utilization of these high molecularweight black oils, as a source of more valuable liquid hydrocarbonproducts, is precluded by present-day refining techniques, dueespecially to the exceedingly high sulfur and asphaltic concentrations.The conversion of a significant proportion of the charge stock intodistillable hydrocarbons-Le., those boiling below about 1150" F.-hashitherto been totally nonfeasible from an economic standpoint. Yet, theabundant supply virtually demands such conversion, especially as a meansfor satisfying the ever-increasing need for greater volumes of the lowerboiling distillables, particularly those within the gasoline boilingrange.

The process of the present invention is directed toward the catalyticconversion of black oils into distillable hydrocarbons boiling in thegasoline boiling range in volumetric yields of 100.0% or more, basedupon the 3,445,377 Patented May 20, 1969 "ice volume of charge stock.Specific examples of the black oils, illustrative of those to which thepresent scheme is applicable, include a vacuum tower bottoms producthaving a gravity of 7.l API at 60 F., containing 4.05% by weight ofsulfur and 23.7% by weight of asphaltics; a topped Middle-East Kuwaitcrude oil, having a gravity of 11.0 API at 60 F., containing 10.1% byweight of asphaltenes and 5.20% by weight of sulfur; and, a vacuumresiduum having a gravity of 8.8 API at 60 F., containing 3.0% by weightof sulfur and 4300 p.p.m. of nitrogen and having a 20.0% volumetricdistillation point of l055 F. The present invention affords theconversion of the majority of such material into gasoline boiling rangedistillable hydrocarbons, heretofore having been considered virtuallyimpossible to achieve on an economically feasible basis. The principaldiiculty resides in the lack of a suitable technique for producing lowerboiling products, substantially free from sulfur and other contaminants,in the presence of the asphaltic material. This asphaltic materialconsists primarily of high molecular weight, nondistillable cokeprecursors, insoluble in light hydrocarbons such as pentane or heptane,which are often found to be complexed with nitrogen, metals and sulfur.Generally, the asphaltic material is dispersed within the crude oil,and, when subjected to elevated ternperatures, has the tendency toocculate and polymerize whereby the conversion thereof to more valuableoilsoluble products becomes extremely diflicult. Thus, the heavy bottomsfrom a crude oil vacuum distillation column (vacuum residuum), indicatesa Conradson carbon residue factor of, for instance, 16.0% by Weight.Such a material is useful only as road asphalt, or `as an extremely lowgrade fuel when cutback with distillate hydrocarbons such as kerosene,light gas oil, etc.

PRIOR ART Heretofore, in the field of catalytic processing of suchhydrocarbonaceous material, two principal approaches have been advanced:liquid-phase hydrogenation and vapor-phase hydrocracking. In the formertype of process, liquid phase oil is passed upwardly, in admixture withhydrogen, into a xed-uidized catalyst bed, or slurry of sub-dividedcatalyst. Although perhaps effective in converting at least a portion ofthe oil-soluble organometallic complexes, this type process isrelatively ineffective with respect to asphaltics which are dispersedwithin the charge. Furthermore, since the hydrogenation reaction zone isgenerally maintained at an elevated temperature of at least about 500(932 R), the retention of unconverted asphaltics, suspended in a freeliquid phase oil for an extended period of time, results in additionalilocculation and agglomeration, making conversion thereof substantiallymore diicult. This type process requires an attendant high capacityregeneration system in order to implement the process on a continuousbasis. Briey, the present invention encompasses a method whereby theasphaltic material is maintained in a dispersed state within a liquidphase rich in hydrogen. This material cornes into intimate contact witha catalyst capable of effecting reaction between the hydrogen andasphaltic material; the liquid phase is itself dispersed in ahydrogen-rich gas phase so that the dissolved hydrogen is continuallyreplenished. The two-fold dispersion and rapid, intimate contacting withthe catalytic surface overcome the difliculties encountered in previousprocesses whereby excessive residence times and depletion of localizedhydrogen supply permit agglomeration of asphaltics and other highmolecular weight species. Such agglomerates are even less available tohydrogen and are not, therefore, susceptible to catalytic reaction. Theyeventually form coke which becomes deposited on the catalyst, therebyfurther reducing catalytic activity within the system.

3 OBJECTS AND EMBODIMENTS The principal object of the present inventionis to provide an economically feasible catalytic process for convertingblack oils into distillable hydrocarbons of lower molecular weight andboiling range. A corollary objective is to maximize the production ofgasoline boiling hydrocarbons from black oils boiling above the normalgasoline boiling range.

Another object is to convert sulfur-contaminated heavy hydrocarboncharge stocks, a significant proportion of which boils in the rangeabove a temperature of 1050 F., into lower-boiling distillablehydrocarbon products of significantly reduced sulfur concentration.

Another object of my invention is to provide a process forthe conversionof black oils having a gravity, API, less than about 25.0, andespecially to produce distillable hydrocarbons from charge stocks, orportions thereof, having an API gravity less than about 10.0.

Still another object is to provide a multiple-stage catalytic processfor the conversion of black oils into gasoline boiling rangehydrocarbons in volumetric yields greater than 100.0%, based upon thefresh charge stock.

Therefore, in a broad embodiment, theA present invention involves aprocess for the conversion of an asphaltenecontaining, sulfuroushydrocarbon charge stock into lowerboiling hydrocarbon products, whichprocess comprises the steps of: (a) admixing said charge stock with anormally liquid hydrocracked product efiluent and separating theresulting mixture to provide an asphaltene-containing heavy fractionhaving an initial boiling point above about 350 F.; (b) introducing saidfraction into one side of a subatmospheric, sectioned flash chamber andwithdrawing a first liquid phase from said side; (c) reacting said firstliquid phase with hydrogen at a temperature above about 700 F. and apressure greater than about 1000 p.s.i.g. in a first catalytic reactionzone, and separating the resulting reaction zone effluent in a firstseparation zone, at substantially the same pressure and at a temperatureabove about 700 F., to provide a second liquid phase and a first vaporphase; (d) introducing at least a portion of said second liquid phaseinto a second side of Said subatmospheric sectioned flash chamber,removing an asphaltene-containing residuum fraction from said secondside and a second vapor phase from an upper, nonsectioned portion ofsaid flash chamber; (e) separating said first vapor phase in a secondseparation zone, at a temperature of from l60 F. to about 140 F. and apressure substantially the same as said first separation zone, toprovide a third liquid phase and a hydrogen-rich third vapor phase, andrecycling at least a portion of the latter to combine with said firstliquid phase; (f) combining said third liquid phase with said secondvapor phase and reacting the resulting mixture with hydrogen in a secondcatalytic reaction zone at conditions selected to convert nitrogenousand sulfurous compounds into hydrogen sulfide, ammonia and hydrocarbons,and to produce lower molecular weight normally liquid hydrocarbons; (g)reacting at least a portion of the resulting second reaction zoneeffluent in a third catalytic reaction zone at hydrocracking conditionsand in contact with a hydrocracking catalytic composite; (h) separatingthe resulting third reaction zone effluent, at a temperature of fromabout 60 F. to about 150 F., in a third separation zone to provide ahydrogen-rich fourth vapor phase and a fourth normally liquidhydrocarbon phase; and, (i) combining said fourth liquid phase with saidcharge stock and separating the resulting mixture as aforesaid.

Other embodiments of my invention reside in particular operatingconditions and the use of specific internal recycle streams. The latterinclude recycle of the hydrogen-rich third gaseous phase to combine withthe fresh charge stock prior to reacting the same in the conversionzone. In the specific example which follows, this gaseous phaseconstitutes more than about 80.0% hydrogen. At least a portion of thesecond liquid phase is diverted and combined with the first liquid phaseand hydrogen, serving in part as a solvent stream to keep the nativeasphaltics dispersed and available to both hydrogen and catalyst in thereaction zone. In a preferred embodiment, a second portion of the secondliquid phase is cooled and recycled to the inlet of the first separationzone to serve as a quench of the reaction zone effluent such that thetemperature in said first separation zone is maintained below a maximumlevel of 760 F. Thus, the first separation zone is controlled at atemperature Within the range of from about 700 F. to about 760 F. Alower temperature permits ammonium salts, resulting from the conversionof nitrogenous compounds, to fall into the liquid phase, whereas ahigher temperature permits the heavier hydrocarbons to be carried overwith the vapor phase. The quantity of this second liquid phase beingrecycled to combine with the charge to the first reaction zone issufilcient to maintain a combined feed ratio in the range of 1:5 toabout 3:5.

The hydrogen-rich fourth vapor phase is recycled to combine with thenormally liquid hydrocarbon charge to the second catalytic reactionzone. In a particularly preferred embodiment, the mixture of freshcharge stock and the hydrocracked product efiluent, or the fourth liquidphase, is initially separated to provide a heavy fraction and amiddle-distillate boiling range fraction-ie., having an initial boilingpoint of about 400 F. and an end boiling point of about 650 F. Thismiddle-distillate fraction is then introduced, as part of the normallyliquid hydrocarbon charge, into the second catalytic reaction zone,Other objects and embodiments will become apparent from the followingfurther description of the present process, particularly the descriptionof the illustrated embodiment in the accompanying drawing.

SUMMARY OF INVENTION Since the hot heavy oil from'the conversion zonecan give rise to serious emulsification problems, the hot separator(first separation zone) is employed to separate the heavy oil as aliquid phase from a vapor phase containing lighter hydrocarbons,hydrogen and water. This hot separator is maintained at essentially thesame pressure as the reaction zone and at essentially the temperature ofthe reaction zone effluent; as above set forth, in a preferredembodiment, the temperature is controlled in the range of about 700 F.to about 760 F.

A hot flash zone functions at a significantly reduced pressure of fromsubatmospheric to about p.s.i.g., and may comprise a low-pressure flashzone-ie. about 60 p.s.i.g.-in combination with a vacuum columnmaintained at about 50-60 mm. of Hg absolute. The hot flash systemserves to eliminate further the difiiculties stemming fromemulsification problems by providing a residuum fraction containing theunconverted asphaltics and a significant amount of those sulfurouscompounds of exceedingly high molecular weight which are not convertedin the first catalytic reaction zone. In addition, subsequentseparations and product recovery facilities are greatly simplified. Ashereinafter described in more detail, the hot flash zone is sectioned,in the lower portion thereof, by means of an imperforate plate. There isprovided, thereby, two individually distinct flash zones, into one ofwhich the heavy fraction, resulting from the initial separation of themixture of charge stock and hydrocracked product eflluent, isintroduced. Some of the mixture will flash into the upper distillationportion of the flash zone, which portion is commonly shared, or in opencommunication with the second side of the flash zone, into which theliquid phase from the hot separator is introduced.

Before describing the process with reference to the accompanyingdrawing, several definitions are believed necessary in order that aclear understanding of the present invention be afforded. In the presentspecification and the appended claims, the phrase pressure substantiallythe same as, is intended to connote that pressure under which asucceeding vessel is maintained, allowing only for the pressure dropexperienced as a result of the ow of fluids through the system. Forexample, where the conversion zone pressure, measured at the inletthereof is 2650 p.s.i.g., the hot separator will function at about 2530p.s.i.g. Similarly, unless otherwise specified, the phrase temperaturesubstantially the same as, is used to indicate that the only reductionin temperature stems from normally experienced loss due to the ow ofmaterial from one piece of equipment to another, or from conversion ofsensible heat to latent heat by flashing where a pressure drop occurs.

The phrase, hydrocarbons boiling within the gasoline boiling range, orgasoline boiling range hydrocarbons, is intended to connote thosehydrocarbons boiling up to a temperature in the range of 350 F. to about450 F., including C5-hydrocarbons, and, as is common in some localities,C4-hydrocarbons. However, for the purpose of more clearly dening thecomponent yields of the present process, gasoline will allude to a C5400F. hydrocarbon fraction, notwithstanding that commercially-scaled unitsin various locales will raise or lower the end boiling point as dictatedby the then current requirements.

Likewise, a black oil is intended to connote a hydrocarbonaceous mixtureof which at least about 10.0% boils above a temperature of about 1050oF., and which has a gravity, API, of 25.0 or less. The greaterproportion of such black oils contains 60.0% `or more of materialboiling above 1050 F., and in many instances, the material is consideredtotally nondistillable. Distillable hydrocarbonsl are those normallyliquid hydrocarbons, including pentanes, having boiling points belowabout 1150 F. Conversion conditions are intended to be those conditionsimposed upon the rst reaction zone in order to convert a substantialportion of the black oil to distillable hydrocarbons. The conversionconditions, within this rst reaction zone, are intended to includetemperatures above about 700 F., with an upper limit of about 800 F.,measured at the inlet to the catalyst bed. Since the bulk of thereactions are exothermic, the temperature increases through the catalystbed, and the reaction zone effluent will be at a higher temperature. Inorder that catalyst stability be preserved, it is preferred to controlthe inlet temperature such that the effluent temperature does not exceedabout 900 F. Hydrogen is admixed with the first reaction zone chargestock, by means of compressive recycle, in an amount generally less thanabout 30,000 s.c.f./bbl., at the selected operating pressure, andpreferably in an -amount of from about 3000 to about 15,000 s.c.f./bbl., based upon fresh feed. The operating pressure will be greater than1000 p.s.i.g., and generally in the range of about 1500 p.s.i.g. toabout 3500 p.s.i.g. The reactor charge passes through the catalyst at aliquid hourly space velocity (defined as volumes of liquid hydrocarboncharge per hour, measured at 60 F., per volume of catalyst disposed inthe reaction zone) of from about 0.25 to about 2.0, again being basedupon fresh feed. When conducted as a continuous process, it isparticularly preferred to introduced the mixture into the vessel in sucha manner that the same passes through the vessel in downward ilow. Theinternals of the reaction zone may be constructed in any suitable mannercapable of providing the required intimate contact lbetween the liquidcharge stock, the gaseous mixture and the catalyst. In some instances itmay be desirable to provide the reaction zone with a packed bed or bedsof inert material such as particles of granite, porcelain, berl saddles,sand, aluminum or other metal turnings, etc., to facilitate distributionof the charge, or to employ perforated trays or special mechanical meansfor this purpose.

As hereinbefore set forth, hydrogen is employed in admixture with thecharge stock, and preferably in an amount of from about 3000 to about15,000 s.c.f./bbl. The hydrogen-containing gas stream, herein sometimesdesignated as recycle hydrogen, since it is conveniently recycledexternally of the reaction zone, fulfills a number of various functions:it serves as a hydrogenating agent, a heat carrier, and particularly ameans for stripping converted material from the catalytic composite,thereby creating still more available catalytically active sites for theincoming, unconverted hydrocarbon charge stock. There will be a netconsumption of hydrogen; to supplement this, hydrogen is added to thesystem from any suitable external source.

The catalytic composite disposed within the first reaction zone can becharacterized as comprising a metallic component having hydrogenationactivity, which component is composited with a refractory inorganicoxide carrier material of either synthetic or natural origin. Theprecise composition -and method of manufacturing the carrier material isnot considered essential to the present process, although a siliceouscarrier, such as 88.0% alumina and 12.0% silica, or 63.0% alumina and37.0% silica, are ygenerally preferred. Briefly, however, suitablemetallic components having hydrogenation activity are those selectedfrom the group consisting of the metals of Groups VI-B and VIII of thePeriodic Table, as indicated in the Periodic Chart of the Elements,Fisher Scientific Company (1953). Thus, the catalytic composite maycomprise one or more metallic components from the group of molybdenum,tungsten, chromium, iron, cobalt, nickel, platinum, palladium, iridium,osmium, rhodium, ruthenium, and mixtures thereof. The concentration ofthe catalytically active metallic component, or components, is primarilydependent upon the particular metal as |well as the characteristics ofthe charge stock. For example, the metallic components of Group VI-B arepreferably present in an amount within the range of about 1.0% to about20.0% by weight, the iron-group metals in an amount within the range ofabout 0.2% to about 10.0% by weight, whereas the platinum-group metalsare preferably present in an amount within the range of about 0.1% toabout 5.0% by weight, all of which are calculated as if the componentsexisted -within the finished catalytic composite as the elemental metal.

The refractory inorganic oxide carrier material may comprise alumina,silica, zirconia, magnesia, titania, boria, strontia, hafnia, andmixtures of two or more including silica-alumina, alumina-silica-boronphosphate, silica-zirconia, silica-magnesia, silica-titania,alumina-zirconia, alumina-magnesia, alumina-titania, magnesia-zirconia,titaniazirconia, magnesia-titania, silica-alumina-zirconia,silicaalumina-magnesia, silica-alumina-titania, silica-magnesiazirconia,silica-alumina-boria, etc. It is preferred to utilize a carrier materialcontaining at least a portion of silica, and preferably a composite ofalumina, silica and boron phosphate with alumina being in the greaterproportion.

Similarly, the catalytic composites disposed within the second and thirdreaction zones will comprise metallic components from the metals ofGroups VI-B and VIII of the Periodic Table, and compounds thereof, whichcomponents are composited with one or more of the refractory inorganicoxides previously set forth. However, since the catalytic composites inthese two subsequent zones are intended to fulfill somewhat differentfunctions, the

second and third zones will, in most situations, make use of differentcatalysts. The applicability of the present process, particularlyregarding the integration therein of the second and third reactionzones, may be illustrated by la two-stage process, the charge stock towhich is the mixture of the first and second vapor phases ashereinbefore described. The function of the `first reaction zone isessentially two-folds; it serves to concentrate a residuum fractioncontaining sulfur while simultaneously producing distillablehydrocarbons and converting sulfurous and nitrogenous compounds intoammonia, hydrogen sulfide and hydrocarbons. The quantity of sulfurremaining in the distillable fraction will, of course, Ibe dependentupon the characteristics of the fresh black oil charge stock.

Whereas the second reaction zone has disposed therein a catalyticcomposite having its principal activity directed towards nitrogen andsulfur removal, and inherently effects some hydrocracking of the heavierhydrocarbons, the catalyst in the third reaction zone is designedprimarily to promote hydrocracking. The precise character, physical andchemical, of the third zone catalyst is dependent to a large extent uponthe characteristics of the original black oil charge stock, the degreeto which sulfurous and nitrogenous compounds have been converted in thefirst two zones, and whether intermediate removal of ammonia andhydrogen sulfide is intended.

Since the functions to be served within the second and third reactionzones are different, most applications of the present invention willinvolve different operating conditions and different catalysts, althoughnot necessarily. Thus, the charge to the second reaction zone, inadmixture with hydrogen in an amount of about 3,000 to about 15,000s.c.f./bbl. of liquid hydrocarbon charge, is raised to a desiredoperating temperature within the range of about 500 F. to about 1000"F., prior to contacting the catalytic composite. The reactions areeffected under an imposed pressure of about 100 pounds to about 3000pounds per square inch, the hydrocarbon charge stock contacting thecatalytic composite at a liquid hourly space velocity (defined asvolumes of liquid charge per hour per v-olume of catalyst disposedwithin the reaction zone), within the range of from about 0.5 to about10.0. In addition to the effective clean-up of the hydrocarbon chargestock, a significant degree of hydrocarbon conversion 4occurs wherebythe heavier molecular weight hydrocarbons, boiling at a temperature offrom about 700 F. to about 1050 F., and including the higherboilingnitrogenous compounds, are converted, by highly selective crackingreactions into lower yboiling hydrocarbons, from which the nitrogen ismore readily removed. The conversion reactions are such that very littlelight, straight-chain paraflinic hydrocarbons are produced.

The catalyst disposed within the second reaction zone serves a dualfunction; that is, the catalyst is non-sensitive to the presence of bothnitrogenous compounds and sulfurous compounds, while at the same time iscapable of effecting the destructive removal thereof, and, ashereinabove set forth, the conversion of at least a portion of thosehydrocarbons boiling at a temperature above about 700 F. A catalystcomprisng comparatively large quantities of molybdenum, calculated asthe element, composited with the carrier material of silica and fromabout 60.0% to about 78.0% by weight of alumina, is very ecient incarrying out the desired operation. A preferred catalytic composite, forutilization in this reaction zone, comprises from about 4.0% to about45.0% by weight of molybdenum. In addition to minor amounts of nickel,from about 0.2% to about 10.0% by weight, like quantities of cobaltand/or iron may be employed in combination with the relatively largeamounts of molybdenum.

As hereinbefore stated, there may or may not be separation facilitiesbetween the second and third reaction zones, for the purpose of removingammonia and hydrogen sulfide from the second reaction zone producteffluent. The preferred scheme, from the viewpoint both of economics andease of operation, is to introduce the total eiliuent into the thirdreaction zone without intervening separation. The obvious advantage isthe elimination of additional separation equipment between` the twoinvolved reaction zones. Such a series-type flow also requires one lesscompressor for hydrogen circulation since the hydrogen may be recycledfrom the eiuent of the third zone to the charge to the second zone.Furthermore, the cost of utilities attributable to heating issignificantly reduced since there is no intentional condensation orcooling of the second zone effluent aside from that resulting viaradiation loss. The particular scheme selected is, of course, dependentupon a number of variables including economic considerations and theprecise character or the catalytic composite disposed within the thirdreaction zone.

At least a portion of the effluent from the second reaction zone isintroduced into the third recation zone at a temperature within therange of about 500 F. to about 950 F. Due to the characteristics of thecharge stock to the third reaction zone, the `operating conditionswithin the same are relatively mild. The third reaction zone ismaintained under an imposed pressure within the range of about to about3000 p.s.i.g., and preferably from about 1000 p.s.i.g. to about 2500p.s.i.g. The rate of hydrocarbon charge will be within the range of fromabout 0.25 to about 5.0 liquid hourly space velocity. Catalyticcomposites which comprise at least one metallic component selected fromGroups VI-B and VIII of the Periodic Table, and a composite of silicaand from about 12.0% to about 30.0% by weight of alumina, constitutesuitable hydrocracking catalysts for use in the conversion of thenitrogenous compound-free charge stock into lower `boiling hydrocarbonproducts. The total quantity of catalytically active metallic componentsis within the range of from 0.1% to about 20.0% by weight of the totalcatalyst. The Group VI-B metal, such as chromium, molybdenum, ortungsten, is usually present within the range of from about 0.5% toabout 10.0% by weight of the catalyst. The Group VIII metals, which maybe divided into two sub-groups, are present in an amount of from 0.1% toabout 10.0% by weight of the total catalyst. When an iron subgroup metalsuch as iron, cobalt, or nickel, is employed, it is present in an amountof from about 0.2% to about 10.0% by weight, while, if a noble metalsuch as platinum, palladium, iridium, etc., is employed, it is presentwithin an amonut within the range of from about 0.1% to about 5.0% byweight of the total catalyst. Suitable catalysts, for utilization withinthe hydrocracking reaction zone, include, but are not limited to thefollowing: 6.0% by weight of nickel and 0.2% by weight of molybdenum;6.0% by weight of nickel; 0.4% by weight of palladium; 6.0% by weight ofnickel and 0.2% by weight of palladium; 6.0% eby weight of nickel and0.2% by weight of platinum; etc. Where appropriate, these metalliccomponents may be impregnated, or ion-exchanged, upon a crystallinealuminosilicate molecular sieve, a variety of which are commonlyreferred to in the art by the broad term zeolites For example, one suchcatalyst, which exhibits the desired characteristics of stability andactivity, is a composite of 5.3% by weight of nickel and a syntheticallyprepared faujasite distributed throughout a silica matrix. The totaleffluent from the third reaction zone is introduced into ahigh-pressure, low-temeprature--i.e., 60 F. to about 140 F.-receiverfrom which a hydrogen-rich gaseous phase is withdrawn and recycled. Thenormally liquid hydrocarbon phase, containing some light parans andbutanes, is admixed with the fresh black oil charge stock for separationas herenbefore set forth.

Other conditions and preferred operating techniques will be given inconjunction with the following description of the present process. Infurther describing this process, reference will be made to theaccompanying figure which illustrates a specific embodiment. In thedrawing, the embodiment is presented by means of a simplified flowdiagram in which such details as pumps, instrumentation and controls,heat-exchange and heat-recovery circuits, valving, start-up lines andsimilar hardware have been omitted as being non-essential to anunderstanding of the techniques involved. The use of such miscellaneousappurtenances, to modify the process, are well within the purview of oneskilled in the art.

DESCRIPTION OF DRAWING For the purpose of demonstrating the illustratedembodiment, the drawing will be described in connection with theconversion of a whole crude black oil charge stock in a commerciallyscaled unit. It is to be understood that the charge stock, streamcompositions, operating con- Table I.-Charge stock properties Gravity,API at 60 F.

Sulfur, wt. percent 2.1 Nitrogen, p.p.m. 1,950

Conradson carbon residue, wt. percent 6.7 Total metals, p.p.m. 36Heptane-insolubles, wt. percent 1.0

An ASTM distillation of the black oil indicates that about 11.5% byvolume has a 400 F. end point, 19.4% is middle-distillate boiling from400 F. to 650 F. and 69.1% boils above 650 F. The 50.0% distillationtemperature is about 905 F., and 35.0% boils above a temperature of 1030F. The unit is designed to process 2,000 bbl/day of fresh charge stock,and it is intended to maximize the ultimate yield of 400 F. end pointgasoline, including butanes for their blending value.

The charge in line 1 is admixed with the normally liquid portion of ahydrocracked product eluent in line 34. The mixture continues throughline 1 into product separation zone 2. Although indicated as a singlevessel for the purpose of simplifying the illustration, productseparation zone 2 may take the form of multiple fractionations and/ordistillations designed to facilitate the recovery of one or morecomponents or streams in a substantially pure state. In any event,product separation is conducted at conditions of pressure andtemperature such that a heavy fraction containing asphaltenes andboiling above 400 F. is removed via line 3. The initial boiling point ofthis heavy fraction is obviously dependent upon the desired end point ofthe ultimate gasoline product.

The heavy fraction continues through line 3 into one side of asubatmospheric, sectioned flash zone 4 which is maintained at a pressureof about 50-60 mm. of Hg absolute. Hot ash zone 4 is sectioned in thelower portion thereof by means of imperforate plate 5 which providesindividual ash zones into one of which the heavy fraction in line 3 isintroduced. As hereinafter set forth, a portion of the first reactionzone product is introduced into the second side of flash zone 4 by wayof line 14. A residuum fraction in an amount of about 142 bbl/day andhaving an API gravity of 2.0, is removed via line 41. It should be notedthat the residuum fraction, which contains the unconverted highmolecular weight asphaltics, is withdrawn from that side of hot flashzone 4 into which the reaction zone eflluent is introduced. A syntheticcrude stream, containing the native or straight-run asphaltenes isremoved via line 6 from that side of the hot flash zone into which theheavy fraction was introduced via line 3. It should further be notedthat imperforate plate S extends only through a lower portion of flashzone 4, so that the upper portion of the latter, which may be suitablyequipped with side-to-side pans, is shared in `common as distillationmeans by the two lower sections formed by imperforate plate 5. The useof sectioned llash zone 4 in the foregoing manner stems from recognitionof the fact that the character of native asphaltenes (or straightrunasphaltics) is significantly different from those residual asphalticswhich have been subjected to reaction conditions, but remain unconvertedto soluble hydrocarbons. Basically, the former are characterized by ahydrogen/ carbon atomic ratio of about 1.0, although in some instancesthe ratio can be higher, Whereas the residual asphaltics have ahydrogen/ carbon atomic ratio less than 1.0, and often as low as 0.75.For example, analyses have indicated that the native asphaltics in acrude tower bottom product comprise 84.15% carbon and 7.23% hydrogen,and have a hydrogen/carbon atomic ratio of 1:02. The residualasphaltics, following an initial treatment of tthis stock, contained91.16% carbon and 5.93% hydrogen, and indicated a hydrogen/carbon atomicratio of 0:77. The principal function, therefore, of the sectional hotflash zone is to provide a charge to the first reaction zone which ishighly concentrated in the straightrun asphaltics compared to theresidual cracked asphaltics. Stream 6 will be more concentrated in thestraight-run asphaltics after being admixed with a portion of the firstreaction zone effluent in line 13, thereby forming the liquid charge tothe first reaction zone. The sectioned flash zone also avoids thenecessity of installing a second such zone for the purpose ofconcentrating the residual asphaltics in line 14.

The amount of liquid phase from hot separator 12, which continuesthrough line 13 to be admixed with the synthetic crude in line 6, issuch that the combined feed ratio is about 2.0. The liquid mixture iscombined with 10,000 s.c.f./bbl. of hydrogen from line 7, based upon thesynthetic crude only, and, following suitable heat exchange with variouseffluent streams not illustrated, continuous through line 6, into heater8 wherein the temperature is increased to a level such that the reactor10 inlet temperature is about 725 F. The heated mixture leaves Iheater 8via line 9, and enters first reaction zone 10 at a LHSV of 0.5, basedupon t-he synthetic crude only. Reaction zone 10' is maintained under animposed pressure of about 3,000| p.s.i.g. The reaction product eflluent,at a temperature of about 825 F., is withdrawn via line 11, and ispassed thereby into hot separation one 12 yat a pressure somewhat lessthan 3,000 p.s.i.g., the drop in pressure being due solely to fluid flowthrough the system. After its use as a heat-exchange medium, theeflluent is introduced into zone 12 at a temperature of 750 F. Aprincipally vaporous phase is withdrawn from the hot separator 12through line 15, and a principally liquid phase is withdrawn via line13. A portion of this liquid phase, in this instance 756 bbl/day,continues via line 13 to combine with the synthetic crude in line 6. Theremaining portion is diverted through line 14 into a hot flash zone y4.The greater proportion of the vapor phase in line 15 consists ofhydrocarbonaceous material boiling below about 700 F., while the liquidphase in line 13 is principally 700 F.plus hydrocarbonaceous material.

In the illustrated embodiment, the material in line 14 enters the hotflash zone 4 at a temperature of about 730 F., the zone being at asubatmospheric pressure of about 50' mm. of Hg absolute. A residuumfraction, having an average molecular weight above 8-50, `and a gravityof 2.0 API, is removed via line 41 in an amount of about 9.2 wt. percento'f the fresh hydrocarbon charge (about 8.0% by volume). A secondprincipally vaporous fraction is removed through line 35. The vaporphase in line 15 is introduced into cold separator 16 which is at a'temperature of about 801 F. Cold separator 16 serves as the pressurecontrol point of the first reaction zone, the control maintaining lapressure of about 3,000I p.s.i.g. on reactor 10. A principally vaporousphase is withdrawn from cold separator 16 through line 17 by means ofcompressor 19. This hydrogen-rich stream is recycled via line 7 to4combine with the normally liquid charge in line 6. Makeup hydrogen, tocompensate for that consumed in reactor 10 as well as subsequentreaction zones, is introduced from any suitable external source via line18. Although indicated as entering the process upstream of compressor19, it is understood that the same may enter the process llo'w at anysuitable point as may be dictated by various engineering considerations.A component analysis of the eflluent from reactor 10` (exclusive of anyrecycled material) is presented in the following Table II, whichreflects a hydrogen consumption of 0.7% by Weight `of the fresh chargein line 1.

11 Table II.-Analysis, reactor 10 effluent Component: Wt. percentAmmonia 01.07 Hydrogen sulfide 1.13

Methane 0.35 Ethane 0.36

Propane 0.48

Butanes :46

Pentanes 0.34

'Hexanes 0.62

(2q-400 F. 3.36 400 F.-650 F. 9.10 650 F.-l050 F. 21.03 Residuum 9.15

1 Weight percent of fresh charge 1n line 1.

With reference once again to the drawing, a third liquid phase iswithdrawn from cold separator 16 via line 20, is combined with thesecond vapor phase from ash zone 4, line 35, and a hydrogen-rich recyclegas phase in line 22, the mixture continuing through line 20 into heater21. After the temperature has been raised to about 650 F., the mixturepasses through line 25 into a second catalytic reaction zone 26. Thenormally liquid feed to reactor 26 is about 2667 bbl./day at a combinedfeed ratio of about 1.6, and contacts the catalytic composite at aliquid hourly space velocity of about 1.05 (exclusive of recyclematerial). The pressure maintained on reactor 26 is somewhat higher than1750 p.s.i.g. The reactor elliuent is Withdrawn via line 27, and, wherenecessary, passes into heater 28. Component analyses of reactor 26eflluent, exclusive of recycled material, are presente-d in thefollowing Table III, and reflects a hydrogen consumption therein of1.22% by weight of the fresh charge stock in line 1.

Table IIL-Analysis, reactor 26 efluent 1 Weight percent of fresh chargein line 1.

These data indicate that the remainder of the sulfurous and nitrogenouscompounds have been converted, and that a significant quantity of lowerboiling hydrocarbons have been produced.

In many instances, the eluent-from reactor 26 will be at a highertemperature in line Z7 than is desired at the inlet to reactor 30. Insuch a situation, it is conceivable that heater 28 could be eliminated.However, since common practice dictates utlizing reactor 26 effluent asa heat-exchange medium, whereby its temperature is lowered, at leastsome heat will be required to raise the temperature. This isaccomplished by Way of heater 28, which will have an extremely lowheater duty in any case; the heated stream passing via line 29' intoreactor 30 at a temperature of about 700 F. The analysis of the reactor30 eluent in line 31 is presented in the following Table 1V. A hydrogenconsumption of 1.29% by weight, of the fresh charge stock in line 1, isreflected inthe Table.

12 Table lV.-Analysis, reactor 30 eluent 1 Weight percent of freshcharge stock ln line 1.

The figures presented do not include about 1,000 bbl./ day of 400 F.plushydrocarbon recycle as hereinafter described.

Reactor 30 product effluent is condensed and passed into cold separator32, via line 31, at a temperature of about F. A hydrogen-rich gaseousphase is withdrawn therefrom via. line 33, and is recycled by way ofcompressor 24, through line 22, to combine lwith the charge to reactor26 in line 20. To compensate for the 2.51% by weight of hydrogenconsumed in reactors 26 and 30, makeup hydrogen is diverted from line 18through line 23 into line 22. A fourth liquid phase hydrocracked eluentpasses through line 34, is combined with the fresh black oil charge inline 1, and the mixture introduced into product separation zone 2.

Product separation is effected to segregate a light hydrocarbon streamin line 36, a butane-rich stream in line 37, a pentane-hexane stream inline 38 and a Gly-400 F. gasoline fraction in line 39. The 400 F.plusmaterial, including native asphaltenes, is removed via line 3, and ispassed into hot flash zone 4 as previously described. In one embodimentof my invention, finding primary utility in the processing of heavierIblack oils, a middle-distillate, 400 F.-650 F. fraction is withdrawnfrom product separation zone 2 via line 40, to be introduced intoreactor 26 `by way of lines 35 and 20. An added advantage, not`withstanding a somewhat higher product separation cost, resides in asignificantly reduced hot flash zone which costs more dollars/barrel ofcapacity than fractionation facilities. Obviously, it is within thescope of my invention to divert a portion of the middle-distillate inline 40 into line 3 for introduction into flash zone 4.

To summarize the results, the overall product distribution 1s presentedin the following Table V:

TABLE V.-oVERALL PRODUCT DISTRIBUTION Component Wt. percent Vol. percentHydrogen Ammonia A summary in terms of bbL/day of the major streams inthe foregoing described process is herein presented for furtherclarification and description of the illustrated embodiment. On thebasis of a fresh charge stock rate of 2,000 bbL/day in line 1: 230bbL/day is 400 F. end point straight run gasoline, which is recovered inline 39, along with 1218 bbl/day of product gasoline; 1770 bbL/dayconstitute the 400 F. reduced crude, which is Withdrawn in line 3 incombination with about 1,000 bbl/day of a 400 F.plus recycle; theresiduum fraction is 142 bbL/day; the charge to reactor 10 in line 6 is1512 bbl/day, of which 756 bbl/day is recycle from hot separator 12; theeiuent from reactor 10 is 1551 bbl./day, and the charge to reactor 26 is2667 bbl/day; the effluent from reactor 26 is 3018 bbL/day, and thetotal charge to product separation is 5018 bbl/day; and, the butaneconcentrate is in an amount of 322 bbl./ day, while the pentane-hexanefraction is recovered in an amount of 478 bbl./day.

Of further interest is the fact that the residuum fraction contains2.07% by weight of sulfur which, when considered in conjunction with the2.23% by weight of hydrogen sulfide, indicates that the product streamsare substantially sulfur-free, and, therefore, are Well-suited forfurther processing. Also, the butane stream is 70.0% iso-butane whilethe pentanes in the pentane-hexane c011- centrate are 93.0% isopentane.This further enhances the value of these products.

The foregoing specification and examples indicate the method by whichthe present process is effected, and illustrate some of the benefitsafforded through the utilization thereof. The present process has beenshown to be a valuable tool to petroleum refining in its ability toconvert black oils into more valuable distillable hydrocarbon products.

I claim as my invention:

1. A process for the conversion of an asphaltene-containing, sulfuroushydrocarbon charge stock into lowerboiling hydrocarbon products whichcomprises the steps of:

(a) admixing said charge stock with a principally liquid hydrocrackedproduct efuent and separating the resulting mixture to provide anasphaltene-containing heavy fraction having an initial boiling pointabove about 350 F.;

(-b) introducing said fraction into one side of a subatmosphericsectioned flash chamber and withdrawing a first liquid phase from saidside;

(c) reacting said rst liquid phase with hydrogen at a temperature aboveabout 700 F. and at a pressure greater than about 1000 p.s.i.g. in afirst catalytic reaction zone, and separating the resulting reactionzone eiuent in a first separation Zone, at substantially the samepressure and at a temperature above about 700 F., to provide a secondliquid phase and a first vapor phase;

(d) introducing at least a portion of said second liquid phase into asecond side of said subatmospheric sectioned ash chamber, removing anasphaltene-containing residuum fraction from said second side and asecond vapor phase from an upper, nonsectioned portion of said ashchamber;

(e) separating said first Vapor phase in a second separation zone, at atemperature of from 60 F. to about 140 F. and a pressure substantiallythe same as said first separation zone, to provide a third liquid phaseand a hydrogen-rich third vapor phase, and recycling at least a portionof the latter to combine with said first liquid phase;

(f) combining said third liquid phase with said second vapor phase andreacting the resulting mixture with hydrogen in a second catalyticreaction zone at conditions selected to convert sulfurous andnitrogenous compounds into hydrogen sulfide, ammonia and hydrocarbon,and to produce lower molecular weight hydrocarbons;

(g) reacting at least a portion of the resulting seco-nd reaction zoneefiiuent in a third catalytic reaction zone at hydrocracking conditionsand in contact with a hydrocracking catalytic composite;

(h) separating the resulting third reaction zone efiiuent, at atemperature of from about F. to about 140 F., in a third separation zoneto provide a hydrogenrich fourth vapor phase and a fourth normallyliquid hydrocarbon phase; and,

(i) combining said fourth liquid phase with said charge stock andseparating the resulting mixture as aforesaid.

2. The process of claim 1 further characterized in that said secondliquid phase is combined with said first liquid phase in an amount toproduce a combined feed ratio to said first reaction zone of from about1.5 to about 3.5.

3. The process of claim 1 further characterized in that the temperatureof the first reaction zone eiliuent, introduced into said firstseparation zone, is within the range of from about 700 F. to about 760F.

4. The process of claim 1 further characterized in that saidhydrogen-rich fourth vapor phase is recycled to combine with said thirdliquid phase and said second vapor phase.

5. The process of claim 1 further characterized in that said mixture ofcharge stock and fourth liquid phase is separated to provide amiddle-distillate fraction, and combining said middle-distillatefraction with said second vapor phase and said third liquid phase.

6. The process of claim 1 further characterized in that the total secondreaction zone eluent is introduced into said third catalytic reactionzone.

References Cited UNITED STATES PATENTS 3,110,663 11/1963 Miller 208-933,254,018 5/1966 Watkins 208-58 3,364,134 1/1968 Hamblin 208-80 HERBERTLEVINE, Primary Examiner.

U.S. C1. X.R. 208-58, 80, 92

